Ambient Temperature Calculations

As the campus has a large chill water storage facility, chilled water can be produced at night when the ambient temperatures are lower and electric demand is less. You must therefore also calculate the effect of chill water storage on COP when rejecting heat to cooling tower water that is slightly cooler at night. Given this information, when doing the calculations with these lower ambient temperatures found at night, we found that the coefficient of performance is 12.434 as compared to the 10.175 we got when doing the original temperatures. This is because the heat rejection becomes slightly more efficient when the cooling tower is colder at night versus during the day when the temperatures are hotter. As advised by Mr. Mike Larson, we used an average night time temperature of 68 degrees Fahrenheight. This value is a good estimate point for our calculations because during the summer, when warmer day temperatures are especially prevalent, this average nighttime temperature provides a good opportunity to observe the effects of the COP. We would expect to see similar effects on the COP in colder months of the year in Champaign, however the effects on COP may vary dependent on the time of the year. Our calculations are shown below.